1. Field of the Invention
This invention relates generally to on-line stored-program computer systems for controlling industrial processes or the like and more particularly to a control computer system capable to making changes in a program while the computer is actually in control of a process.
2. Description of Prior Art
It is well known in the art that the computer in automated control systems generally contains a control program for controlling a process. It is also well known by engineers and programmers that it is difficult to make changes in the program of a stored-program computer while the computer is actually in control of a real-time process. This is due to the likelihood of errors being made, the effects of which can be disastrous in the process. Frequently, the magnitude of these changes is large which generally signifies that those changes are difficult to implement quickly. The magnitude of the changes also makes it difficult to remove those changes, if their effect on the process under control proves undesirable. Accordingly, it is desirable to provide a method and means for making changes to a program in an orderly way with the option of quickly removing changes to restore the program to its original state while controlling a real-time process.